1. Field of the Invention
The present invention relates to an optically rewritable optical disc and to an apparatus and method for reading addresses prewritten to the optical disc.
2. Description of Related Art
DVD-RAM, CD-RW, and MD are examples of user-recordable optical discs that have become available in the last few years. This type of recordable optical disc has grooves formed along a spiral or plural concentric tracks with a phase change material or magneto-optical material formed on the groove surface. Addresses for specifying a particular location on the disc are also pre-recorded to the tracks using rewritable marks. This type of address is described in Japanese Patent Laid-Open Publication (kokai) H8-315426.
Kokai H8-315426 describes providing discontinuities in the grooves and using these discontinuous parts for forming a pattern corresponding to the address signal. A pattern corresponding to the address signal is a binary signal that inverts at each discontinuity, an on/off signal used for generating an ATIP (Absolute Time Pregroove) signal. The discontinuities are therefore used simply as a signal indicating presence or absence.